1. Field of the Invention
Generally, the present invention relates to the field of fabricating integrated circuits, and, more particularly, to the management of process recipes required for processing different products at different process tools.
2. Description of the Related Art
Integrated circuits are typically manufactured in automated or semi-automated facilities, thereby passing through a large number of process and metrology steps to complete the device. The number and type of process and metrology steps a semiconductor device has to go through depends on the specifics of the semiconductor device to be fabricated. A usual process flow for an integrated circuit may include a plurality of photolithography steps to image a circuit pattern for a specific device layer into a resist layer, which is subsequently patterned to form a resist mask for further processes in structuring the device layer under consideration by, for example, etch or implant processes and the like. Thus, layer after layer, a plurality of process steps are performed based on a specific lithographic mask set for the various layers of the specified device. For instance, a sophisticated CPU requires several hundred process steps, each of which has to be carried out within specified process margins so as to fulfill the specifications for the device under consideration. Since many of these processes are very critical, a plurality of metrology steps have to be performed so as to efficiently control the process flow. Typical metrology processes may include the measurement of layer thickness, the determination of dimensions of critical features, such as the gate length of transistors, the measurement of dopant profiles, and the like. As the majority of the process margins are device specific, many of the metrology processes are specifically designed for the device under consideration and require specific parameter settings at the adequate metrology tools.
In a semiconductor facility, a plurality of different product types are usually manufactured at the same time, such as memory chips of different design and storage capacity, CPUs and the like, wherein the number of different product types may even reach a hundred and more in production lines for manufacturing ASICs (application specific ICs). Since each of the different product types may require a specific process flow, different mask sets for the lithography, specific settings in the various process tools, such as deposition tools, etch tools, implantation tools, CMP (chemical mechanical polishing) tools, and the like, may be necessary.
Hereinafter, the parameter setting for a specific process in a specified process tool or metrology or inspection tool may commonly be referred to as process recipe or simply as recipe. Thus, a large number of different process recipes may be required which have to be applied to the process tools at the time the corresponding product types are to be processed in the respective tools.
To avoid an incorrect processing of a specific product type, which is usually provided in the form of a plurality of substrates referred to as a lot, an automated recipe management system (RMS) database is frequently employed, storing the recipe for each available product type and each available process the product type has to undergo. A combination of a product type at a specific manufacturing stage and a process that may be available for this product type is herein also denoted as context or context point. Establishing and maintaining M times N context points, wherein M may represent the number of process steps and N may represent the number of product types, may result in an immense complexity of the RMS database and may also necessitate great effort in setting up the context point information, that is, the recipe information.
In conventional RMS regimes, therefore, the volume of the set-up information is frequently reduced in that the specific process flow or a part thereof, i.e., a sequence of two or more processes, which may also be denoted hereinafter as a process flow entity or simply an entity, is used as context point rather than employing every single process. Thus, the actual process flow for a specific product type may be divided into a plurality of smaller entities, at least some of which include two or more individual processes. Since, in many cases, several product types share one or more of the process flow entities, establishing the RMS database on the basis of the process flow entities may lower the number of context points required for the entirety of product types and may therefore reduce the complexity in setting up and maintaining the context information. That is, the process flow of each individual product type is to be defined as entries for the RMS database, wherein the process flow entities commonly used by all product types are to be entered only once.
Creating the context points on the basis of process flow entities may, however, not be helpful in reducing effort and complexity of context information relating to process steps that depend on the specifics of the mask set used for manufacturing a certain product type. For instance, the lithography patterning, the majority of metrology and defect inspection processes, a plurality of etch and CMP steps, and the like vary for different mask sets and thus require a separate set-up of context points for each product type, thereby rendering the above-explained approach with process flow entities inefficient, especially when a large number of product types is present in the process line and/or when new product types are frequently introduced. For example, in fabricating microprocessors, a specific product type may frequently be altered with respect to design and/or process recipes to provide minor design alternatives and/or new speed grades of basically the same product type, wherein each new alternative version or speed grade is then to be considered a new product type and requires the set up of new context points in the RMS database, thereby demanding a large amount of manpower of process engineers.
In view of the problems encountered in the conventional technique, an improved method is needed that allows more effective adaptation of process recipes to product types in a semiconductor process line, especially when a large number of different product types are present and/or when new product types are frequently introduced.